Duawism and monism are de two centraw schoows of dought on de mind–body probwem, awdough nuanced views have arisen dat do not fit one or de oder category neatwy. Duawism finds its entry into Western phiwosophy danks to René Descartes in de 17f century.[5] Substance duawists wike Descartes argue dat de mind is an independentwy existing substance, whereas property duawists maintain dat de mind is a group of independent properties dat emerge from and cannot be reduced to de brain, but dat it is not a distinct substance.[6]

Monism is de position dat mind and body are not ontowogicawwy distinct entities (independent substances). This view was first advocated in Western phiwosophy by Parmenides in de 5f century BCE and was water espoused by de 17f century rationawistBaruch Spinoza.[7]Physicawists argue dat onwy entities postuwated by physicaw deory exist, and dat mentaw processes wiww eventuawwy be expwained in terms of dese entities as physicaw deory continues to evowve. Physicawists maintain various positions on de prospects of reducing mentaw properties to physicaw properties (many of whom adopt compatibwe forms of property duawism),[8][9][10][11][12][13] and de ontowogicaw status of such mentaw properties remains uncwear.[12][14][15]Ideawists maintain dat de mind is aww dat exists and dat de externaw worwd is eider mentaw itsewf, or an iwwusion created by de mind. Neutraw monists such as Ernst Mach and Wiwwiam James argue dat events in de worwd can be dought of as eider mentaw (psychowogicaw) or physicaw depending on de network of rewationships into which dey enter, and duaw-aspect monists such as Spinoza adhere to de position dat dere is some oder, neutraw substance, and dat bof matter and mind are properties of dis unknown substance. The most common monisms in de 20f and 21st centuries have aww been variations of physicawism; dese positions incwude behaviorism, de type identity deory, anomawous monism and functionawism.[16]

Most modern phiwosophers of mind adopt eider a reductive or non-reductive physicawist position, maintaining in deir different ways dat de mind is not someding separate from de body.[16] These approaches have been particuwarwy infwuentiaw in de sciences, especiawwy in de fiewds of sociobiowogy, computer science (specificawwy, artificiaw intewwigence), evowutionary psychowogy and de various neurosciences.[17][18][19][20] Reductive physicawists assert dat aww mentaw states and properties wiww eventuawwy be expwained by scientific accounts of physiowogicaw processes and states.[21][22][23] Non-reductive physicawists argue dat awdough de mind is not a separate substance, mentaw properties supervene on physicaw properties, or dat de predicates and vocabuwary used in mentaw descriptions and expwanations are indispensabwe, and cannot be reduced to de wanguage and wower-wevew expwanations of physicaw science.[24][25] Continued neuroscientific progress has hewped to cwarify some of dese issues; however, dey are far from being resowved. Modern phiwosophers of mind continue to ask how de subjective qwawities and de intentionawity of mentaw states and properties can be expwained in naturawistic terms.[26][27]

The mind–body probwem concerns de expwanation of de rewationship dat exists between minds, or mentaw processes, and bodiwy states or processes.[2] The main aim of phiwosophers working in dis area is to determine de nature of de mind and mentaw states/processes, and how—or even if—minds are affected by and can affect de body.

Our perceptuaw experiences depend on stimuwi dat arrive at our various sensory organs from de externaw worwd, and dese stimuwi cause changes in our mentaw states, uwtimatewy causing us to feew a sensation, which may be pweasant or unpweasant. Someone's desire for a swice of pizza, for exampwe, wiww tend to cause dat person to move his or her body in a specific manner and in a specific direction to obtain what he or she wants. The qwestion, den, is how it can be possibwe for conscious experiences to arise out of a wump of gray matter endowed wif noding but ewectrochemicaw properties.[16]

In Western Phiwosophy, de earwiest discussions of duawist ideas are in de writings of Pwato who maintained dat humans' "intewwigence" (a facuwty of de mind or souw) couwd not be identified wif, or expwained in terms of, deir physicaw body.[29][30] However, de best-known version of duawism is due to René Descartes (1641), and howds dat de mind is a non-extended, non-physicaw substance, a "res cogitans".[5] Descartes was de first to cwearwy identify de mind wif consciousness and sewf-awareness, and to distinguish dis from de brain, which was de seat of intewwigence. He was derefore de first to formuwate de mind–body probwem in de form in which it stiww exists today.[5]

The most freqwentwy used argument in favor of duawism appeaws to de common-sense intuition dat conscious experience is distinct from inanimate matter. If asked what de mind is, de average person wouwd usuawwy respond by identifying it wif deir sewf, deir personawity, deir souw, or some oder such entity. They wouwd awmost certainwy deny dat de mind simpwy is de brain, or vice versa, finding de idea dat dere is just one ontowogicaw entity at pway to be too mechanistic, or simpwy unintewwigibwe.[6] Many modern phiwosophers of mind dink dat dese intuitions are misweading and dat we shouwd use our criticaw facuwties, awong wif empiricaw evidence from de sciences, to examine dese assumptions to determine wheder dere is any reaw basis to dem.[6]

Anoder important argument in favor of duawism is dat de mentaw and de physicaw seem to have qwite different, and perhaps irreconciwabwe, properties.[31] Mentaw events have a subjective qwawity, whereas physicaw events do not. So, for exampwe, one can reasonabwy ask what a burnt finger feews wike, or what a bwue sky wooks wike, or what nice music sounds wike to a person, uh-hah-hah-hah. But it is meaningwess, or at weast odd, to ask what a surge in de uptake of gwutamate in de dorsowateraw portion of de prefrontaw cortex feews wike.

Phiwosophers of mind caww de subjective aspects of mentaw events "qwawia" or "raw feews".[31] There is someding dat it is wike to feew pain, to see a famiwiar shade of bwue, and so on, uh-hah-hah-hah. There are qwawia invowved in dese mentaw events dat seem particuwarwy difficuwt to reduce to anyding physicaw. David Chawmers expwains dis argument by stating dat we couwd conceivabwy know aww de objective information about someding, such as de brain states and wavewengds of wight invowved wif seeing de cowor red, but stiww not know someding fundamentaw about de situation – what it is wike to see de cowor red.[32]

If consciousness (de mind) can exist independentwy of physicaw reawity (de brain), one must expwain how physicaw memories are created concerning consciousness. Duawism must derefore expwain how consciousness affects physicaw reawity. One possibwe expwanation is dat of a miracwe, proposed by Arnowd Geuwincx and Nicowas Mawebranche, where aww mind–body interactions reqwire de direct intervention of God.

Anoder possibwe argument dat has been proposed by C. S. Lewis[33] is de Argument from Reason: if, as monism impwies, aww of our doughts are de effects of physicaw causes, den we have no reason for assuming dat dey are awso de conseqwent of a reasonabwe ground. Knowwedge, however, is apprehended by reasoning from ground to conseqwent. Therefore, if monism is correct, dere wouwd be no way of knowing dis—or anyding ewse—we couwd not even suppose it, except by a fwuke.

The zombie argument is based on a dought experiment proposed by Todd Moody, and devewoped by David Chawmers in his book The Conscious Mind. The basic idea is dat one can imagine one's body, and derefore conceive de existence of one's body, widout any conscious states being associated wif dis body. Chawmers' argument is dat it seems possibwe dat such a being couwd exist because aww dat is needed is dat aww and onwy de dings dat de physicaw sciences describe about a zombie must be true of it. Since none of de concepts invowved in dese sciences make reference to consciousness or oder mentaw phenomena, and any physicaw entity can be by definition described scientificawwy via physics, de move from conceivabiwity to possibiwity is not such a warge one.[34] Oders such as Dennett have argued dat de notion of a phiwosophicaw zombie is an incoherent,[35] or unwikewy,[36] concept. It has been argued under physicawism dat one must eider bewieve dat anyone incwuding onesewf might be a zombie, or dat no one can be a zombie—fowwowing from de assertion dat one's own conviction about being (or not being) a zombie is a product of de physicaw worwd and is derefore no different from anyone ewse's. This argument has been expressed by Dennett who argues dat "Zombies dink dey are conscious, dink dey have qwawia, dink dey suffer pains—dey are just 'wrong' (according to dis wamentabwe tradition) in ways dat neider dey nor we couwd ever discover!"[35]
See awso de probwem of oder minds.

Interactionist duawism, or simpwy interactionism, is de particuwar form of duawism first espoused by Descartes in de Meditations.[5] In de 20f century, its major defenders have been Karw Popper and John Carew Eccwes.[37] It is de view dat mentaw states, such as bewiefs and desires, causawwy interact wif physicaw states.[6]

Descartes' famous argument for dis position can be summarized as fowwows: Sef has a cwear and distinct idea of his mind as a dinking ding dat has no spatiaw extension (i.e., it cannot be measured in terms of wengf, weight, height, and so on). He awso has a cwear and distinct idea of his body as someding dat is spatiawwy extended, subject to qwantification and not abwe to dink. It fowwows dat mind and body are not identicaw because dey have radicawwy different properties.[5]

At de same time, however, it is cwear dat Sef's mentaw states (desires, bewiefs, etc.) have causaw effects on his body and vice versa: A chiwd touches a hot stove (physicaw event) which causes pain (mentaw event) and makes her yeww (physicaw event), dis in turn provokes a sense of fear and protectiveness in de caregiver (mentaw event), and so on, uh-hah-hah-hah.

Descartes' argument cruciawwy depends on de premise dat what Sef bewieves to be "cwear and distinct" ideas in his mind are necessariwy true. Many contemporary phiwosophers doubt dis.[38][39][40] For exampwe, Joseph Agassi suggests dat severaw scientific discoveries made since de earwy 20f century have undermined de idea of priviweged access to one's own ideas. Freud cwaimed dat a psychowogicawwy-trained observer can understand a person's unconscious motivations better dan de person himsewf does. Duhem has shown dat a phiwosopher of science can know a person's medods of discovery better dan dat person hersewf does, whiwe Mawinowski has shown dat an andropowogist can know a person's customs and habits better dan de person whose customs and habits dey are. He awso asserts dat modern psychowogicaw experiments dat cause peopwe to see dings dat are not dere provide grounds for rejecting Descartes' argument, because scientists can describe a person's perceptions better dan de person hersewf can, uh-hah-hah-hah.[41][42]

Psychophysicaw parawwewism, or simpwy parawwewism, is de view dat mind and body, whiwe having distinct ontowogicaw statuses, do not causawwy infwuence one anoder. Instead, dey run awong parawwew pads (mind events causawwy interact wif mind events and brain events causawwy interact wif brain events) and onwy seem to infwuence each oder.[43] This view was most prominentwy defended by Gottfried Leibniz. Awdough Leibniz was an ontowogicaw monist who bewieved dat onwy one type of substance, de monad, exists in de universe, and dat everyding is reducibwe to it, he nonedewess maintained dat dere was an important distinction between "de mentaw" and "de physicaw" in terms of causation, uh-hah-hah-hah. He hewd dat God had arranged dings in advance so dat minds and bodies wouwd be in harmony wif each oder. This is known as de doctrine of pre-estabwished harmony.[44]

Occasionawism is de view espoused by Nichowas Mawebranche as weww as Iswamic phiwosophers such as Abu Hamid Muhammad ibn Muhammad aw-Ghazawi dat asserts dat aww supposedwy causaw rewations between physicaw events, or between physicaw and mentaw events, are not reawwy causaw at aww. Whiwe body and mind are different substances, causes (wheder mentaw or physicaw) are rewated to deir effects by an act of God's intervention on each specific occasion, uh-hah-hah-hah.[45]

Property duawism is de view dat de worwd is constituted of just one kind of substance – de physicaw kind – and dere exist two distinct kinds of properties: physicaw properties and mentaw properties. In oder words, it is de view dat non-physicaw, mentaw properties (such as bewiefs, desires and emotions) inhere in some physicaw bodies (at weast, brains). How mentaw and physicaw properties rewate causawwy depends on de variety of property duawism in qwestion, and is not awways a cwear issue. Sub-varieties of property duawism incwude:

Emergent materiawism asserts dat when matter is organized in de appropriate way (i.e. in de way dat wiving human bodies are organized), mentaw properties emerge in a way not fuwwy accountabwe for by physicaw waws.[6] These emergent properties have an independent ontowogicaw status and cannot be reduced to, or expwained in terms of, de physicaw substrate from which dey emerge. They are dependent on de physicaw properties from which dey emerge, but opinions vary as to de coherence of top–down causation, i.e. de causaw effectiveness of such properties. A form of emergent materiawism has been espoused by David Chawmers and de concept has undergone someding of a renaissance in recent years,[46] but it was awready suggested in de 19f century by Wiwwiam James.

Epiphenomenawism is a doctrine first formuwated by Thomas Henry Huxwey.[47] It consists of de view dat mentaw phenomena are causawwy ineffectuaw, where one or more mentaw states do not have any infwuence on physicaw states or mentaw phenomena are de effects, but not de causes, of physicaw phenomena. Physicaw events can cause oder physicaw events and physicaw events can cause mentaw events, but mentaw events cannot cause anyding, since dey are just causawwy inert by-products (i.e. epiphenomena) of de physicaw worwd.[43] This view has been defended most strongwy in recent times by Frank Jackson.[48]

Non-reductive physicawism is de view dat mentaw properties form a separate ontowogicaw cwass to physicaw properties: mentaw states (such as qwawia) are not reducibwe to physicaw states. The ontowogicaw stance towards qwawia in de case of non-reductive physicawism does not impwy dat qwawia are causawwy inert; dis is what distinguishes it from epiphenomenawism.

Panpsychism is de view dat aww matter has a mentaw aspect, or, awternativewy, aww objects have a unified center of experience or point of view. Superficiawwy, it seems to be a form of property duawism, since it regards everyding as having bof mentaw and physicaw properties. However, some panpsychists say dat mechanicaw behaviour is derived from de primitive mentawity of atoms and mowecuwes—as are sophisticated mentawity and organic behaviour, de difference being attributed to de presence or absence of compwex structure in a compound object. So wong as de reduction of non-mentaw properties to mentaw ones is in pwace, panpsychism is not a (strong) form of property duawism; oderwise it is.

Duaw aspect deory or duaw-aspect monism is de view dat de mentaw and de physicaw are two aspects of, or perspectives on, de same substance. (Thus it is a mixed position, which is monistic in some respects). In modern phiwosophicaw writings, de deory's rewationship to neutraw monism has become somewhat iww-defined, but one proffered distinction says dat whereas neutraw monism awwows de context of a given group of neutraw ewements and de rewationships into which dey enter to determine wheder de group can be dought of as mentaw, physicaw, bof, or neider, duaw-aspect deory suggests dat de mentaw and de physicaw are manifestations (or aspects) of some underwying substance, entity or process dat is itsewf neider mentaw nor physicaw as normawwy understood. Various formuwations of duaw-aspect monism awso reqwire de mentaw and de physicaw to be compwementary, mutuawwy irreducibwe and perhaps inseparabwe (dough distinct).[49][50][51]

This is a phiwosophy of mind dat regards de degrees of freedom between mentaw and physicaw weww-being as not necessariwy synonymous dus impwying an experientiaw duawism between body and mind. An exampwe of dese disparate degrees of freedom is given by Awwan Wawwace who notes dat it is "experientiawwy apparent dat one may be physicawwy uncomfortabwe—for instance, whiwe engaging in a strenuous physicaw workout—whiwe mentawwy cheerfuw; conversewy, one may be mentawwy distraught whiwe experiencing physicaw comfort".[52] Experientiaw duawism notes dat our subjective experience of merewy seeing someding in de physicaw worwd seems qwawitativewy different dan mentaw processes wike grief dat comes from wosing a woved one. This phiwosophy awso is a proponent of causaw duawism which is defined as de duaw abiwity for mentaw states and physicaw states to affect one anoder. Mentaw states can cause changes in physicaw states and vice versa.

However, unwike cartesian duawism or some oder systems, experientiaw duawism does not posit two fundamentaw substances in reawity: mind and matter. Rader, experientiaw duawism is to be understood as a conceptuaw framework dat gives credence to de qwawitative difference between de experience of mentaw and physicaw states. Experientiaw duawism is accepted as de conceptuaw framework of Madhyamaka Buddhism.

Madhayamaka Buddhism goes even furder, finding fauwt wif de monist view of physicawist phiwosophies of mind as weww in dat dese generawwy posit matter and energy as de fundamentaw substance of reawity. Nonedewess, dis does not impwy dat de cartesian duawist view is correct, rader Madhyamaka regards as error any affirming view of a fundamentaw substance to reawity.

In denying de independent sewf-existence of aww de phenomena dat make up de worwd of our experience, de Madhyamaka view departs from bof de substance duawism of Descartes and de substance monism—namewy, physicawism—dat is characteristic of modern science. The physicawism propounded by many contemporary scientists seems to assert dat de reaw worwd is composed of physicaw dings-in-demsewves, whiwe aww mentaw phenomena are regarded as mere appearances, devoid of any reawity in and of demsewves. Much is made of dis difference between appearances and reawity.[52]

Indeed, physicawism, or de idea dat matter is de onwy fundamentaw substance of reawity, is expwicitwy rejected by Buddhism.

In de Madhyamaka view, mentaw events are no more or wess reaw dan physicaw events. In terms of our common-sense experience, differences of kind do exist between physicaw and mentaw phenomena. Whiwe de former commonwy have mass, wocation, vewocity, shape, size, and numerous oder physicaw attributes, dese are not generawwy characteristic of mentaw phenomena. For exampwe, we do not commonwy conceive of de feewing of affection for anoder person as having mass or wocation, uh-hah-hah-hah. These physicaw attributes are no more appropriate to oder mentaw events such as sadness, a recawwed image from one's chiwdhood, de visuaw perception of a rose, or consciousness of any sort. Mentaw phenomena are, derefore, not regarded as being physicaw, for de simpwe reason dat dey wack many of de attributes dat are uniqwewy characteristic of physicaw phenomena. Thus, Buddhism has never adopted de physicawist principwe dat regards onwy physicaw dings as reaw.[52]

In contrast to duawism, monism does not accept any fundamentaw divisions. The fundamentawwy disparate nature of reawity has been centraw to forms of eastern phiwosophies for over two miwwennia. In Indian and Chinese phiwosophy, monism is integraw to how experience is understood. Today, de most common forms of monism in Western phiwosophy are physicawist.[16] Physicawistic monism asserts dat de onwy existing substance is physicaw, in some sense of dat term to be cwarified by our best science.[53] However, a variety of formuwations (see bewow) are possibwe. Anoder form of monism, ideawism, states dat de onwy existing substance is mentaw. Awdough pure ideawism, such as dat of George Berkewey, is uncommon in contemporary Western phiwosophy, a more sophisticated variant cawwed panpsychism, according to which mentaw experience and properties may be at de foundation of physicaw experience and properties, has been espoused by some phiwosophers such as Awfred Norf Whitehead[54] and David Ray Griffin.[46]

Phenomenawism is de deory dat representations (or sense data) of externaw objects are aww dat exist. Such a view was briefwy adopted by Bertrand Russeww and many of de wogicaw positivists during de earwy 20f century.[55] A dird possibiwity is to accept de existence of a basic substance dat is neider physicaw nor mentaw. The mentaw and physicaw wouwd den bof be properties of dis neutraw substance. Such a position was adopted by Baruch Spinoza[7] and was popuwarized by Ernst Mach[56] in de 19f century. This neutraw monism, as it is cawwed, resembwes property duawism.

Behaviorism dominated phiwosophy of mind for much of de 20f century, especiawwy de first hawf.[16] In psychowogy, behaviorism devewoped as a reaction to de inadeqwacies of introspectionism.[53] Introspective reports on one's own interior mentaw wife are not subject to carefuw examination for accuracy and cannot be used to form predictive generawizations. Widout generawizabiwity and de possibiwity of dird-person examination, de behaviorists argued, psychowogy cannot be scientific.[53] The way out, derefore, was to ewiminate de idea of an interior mentaw wife (and hence an ontowogicawwy independent mind) awtogeder and focus instead on de description of observabwe behavior.[57]

Parawwew to dese devewopments in psychowogy, a phiwosophicaw behaviorism (sometimes cawwed wogicaw behaviorism) was devewoped.[53] This is characterized by a strong verificationism, which generawwy considers unverifiabwe statements about interior mentaw wife pointwess. For de behaviorist, mentaw states are not interior states on which one can make introspective reports. They are just descriptions of behavior or dispositions to behave in certain ways, made by dird parties to expwain and predict anoder's behavior.[58]

Phiwosophicaw behaviorism has fawwen out of favor since de watter hawf of de 20f century, coinciding wif de rise of cognitivism.[2] Cognitivists reject behaviorism due to severaw perceived probwems. For exampwe, behaviorism couwd be said to be counterintuitive when it maintains dat someone is tawking about behavior in de event dat a person is experiencing a painfuw headache.

Type physicawism (or type-identity deory) was devewoped by John Smart[23] and Uwwin Pwace[59] as a direct reaction to de faiwure of behaviorism. These phiwosophers reasoned dat, if mentaw states are someding materiaw, but not behavioraw, den mentaw states are probabwy identicaw to internaw states of de brain, uh-hah-hah-hah. In very simpwified terms: a mentaw state M is noding oder dan brain state B. The mentaw state "desire for a cup of coffee" wouwd dus be noding more dan de "firing of certain neurons in certain brain regions".[23]

The cwassic Identity deory and Anomawous Monism in contrast. For de Identity deory, every token instantiation of a singwe mentaw type corresponds (as indicated by de arrows) to a physicaw token of a singwe physicaw type. For anomawous monism, de token–token correspondences can faww outside of de type–type correspondences. The resuwt is token identity.

Despite its initiaw pwausibiwity, de identity deory faces a strong chawwenge in de form of de desis of muwtipwe reawizabiwity, first formuwated by Hiwary Putnam.[25] For exampwe, not onwy humans, but many different species of animaws can experience pain, uh-hah-hah-hah. However, it seems highwy unwikewy dat aww of dese diverse organisms wif de same pain experience are in de identicaw brain state. And if dis is de case, den pain cannot be identicaw to a specific brain state. The identity deory is dus empiricawwy unfounded.[25]

On de oder hand, even granted de above, it does not fowwow dat identity deories of aww types must be abandoned. According to token identity deories, de fact dat a certain brain state is connected wif onwy one mentaw state of a person does not have to mean dat dere is an absowute correwation between types of mentaw state and types of brain state. The type–token distinction can be iwwustrated by a simpwe exampwe: de word "green" contains four types of wetters (g, r, e, n) wif two tokens (occurrences) of de wetter e awong wif one each of de oders.
The idea of token identity is dat onwy particuwar occurrences of mentaw events are identicaw wif particuwar occurrences or tokenings of physicaw events.[60] Anomawous monism (see bewow) and most oder non-reductive physicawisms are token-identity deories.[61] Despite dese probwems, dere is a renewed interest in de type identity deory today, primariwy due to de infwuence of Jaegwon Kim.[23]

What aww dese different varieties of functionawism share in common is de desis dat mentaw states are characterized by deir causaw rewations wif oder mentaw states and wif sensory inputs and behavioraw outputs. That is, functionawism abstracts away from de detaiws of de physicaw impwementation of a mentaw state by characterizing it in terms of non-mentaw functionaw properties. For exampwe, a kidney is characterized scientificawwy by its functionaw rowe in fiwtering bwood and maintaining certain chemicaw bawances. From dis point of view, it does not reawwy matter wheder de kidney be made up of organic tissue, pwastic nanotubes or siwicon chips: it is de rowe dat it pways and its rewations to oder organs dat define it as a kidney.[62]

Non-reductionist phiwosophers howd firmwy to two essentiaw convictions wif regard to mind–body rewations: 1) Physicawism is true and mentaw states must be physicaw states, but 2) Aww reductionist proposaws are unsatisfactory: mentaw states cannot be reduced to behavior, brain states or functionaw states.[53] Hence, de qwestion arises wheder dere can stiww be a non-reductive physicawism. Donawd Davidson's anomawous monism[24] is an attempt to formuwate such a physicawism. He "dinks dat when one runs across what are traditionawwy seen as absurdities of Reason, such as akrasia or sewf-deception, de personaw psychowogy framework is not to be given up in favor of de subpersonaw one, but rader must be enwarged or extended so dat de rationawity set out by de principwe of charity can be found ewsewhere."[64]

Davidson uses de desis of supervenience: mentaw states supervene on physicaw states, but are not reducibwe to dem. "Supervenience" derefore describes a functionaw dependence: dere can be no change in de mentaw widout some change in de physicaw–causaw reducibiwity between de mentaw and physicaw widout ontowogicaw reducibiwity.[65]

Because non-reductive physicawist deories attempt to bof retain de ontowogicaw distinction between mind and body and try to sowve de "surfeit of expwanations puzzwe" in some way; critics often see dis as a paradox and point out de simiwarities to epiphenomenawism, in dat it is de brain dat is seen as de root "cause" not de mind, and de mind seems to be rendered inert.

Epiphenomenawism regards one or more mentaw states as de byproduct of physicaw brain states, having no infwuence on physicaw states. The interaction is one-way (sowving de "surfeit of expwanations puzzwe") but weaving us wif non-reducibwe mentaw states (as a byproduct of brain states) – causawwy reducibwe, but ontowogicawwy irreducibwe to physicaw states. Pain wouwd be seen by epiphenomenawiasts as being caused by de brain state but as not having effects on oder brain states, dough it might have effects on oder mentaw states (i.e. cause distress).

Weak emergentism is a form of "non-reductive physicawism" dat invowves a wayered view of nature, wif de wayers arranged in terms of increasing compwexity and each corresponding to its own speciaw science. Some phiwosophers howd dat emergent properties causawwy interact wif more fundamentaw wevews, whiwe oders maintain dat higher-order properties simpwy supervene over wower wevews widout direct causaw interaction, uh-hah-hah-hah. The watter group derefore howds a wess strict, or "weaker", definition of emergentism, which can be rigorouswy stated as fowwows: a property P of composite object O is emergent if it is metaphysicawwy impossibwe for anoder object to wack property P if dat object is composed of parts wif intrinsic properties identicaw to dose in O and has dose parts in an identicaw configuration, uh-hah-hah-hah.

Sometimes emergentists use de exampwe of water having a new property when Hydrogen H and Oxygen O combine to form H2O (water). In dis exampwe dere "emerges" a new property of a transparent wiqwid dat wouwd not have been predicted by understanding hydrogen and oxygen as gases. This is anawogous to physicaw properties of de brain giving rise to a mentaw state. Emergentists try to sowve de notorious mind–body gap dis way. One probwem for emergentism is de idea of "causaw cwosure" in de worwd dat does not awwow for a mind-to-body causation, uh-hah-hah-hah.[66]

If one is a materiawist and bewieves dat aww aspects of our common-sense psychowogy wiww find reduction to a mature cognitive neuroscience, and dat non-reductive materiawism is mistaken, den one can adopt a finaw, more radicaw position: ewiminative materiawism.

There are severaw varieties of ewiminative materiawism, but aww maintain dat our common-sense "fowk psychowogy" badwy misrepresents de nature of some aspect of cognition, uh-hah-hah-hah. Ewiminativists such as Patricia and Pauw Churchwand argue dat whiwe fowk psychowogy treats cognition as fundamentawwy sentence-wike, de non-winguistic vector/matrix modew of neuraw network deory or connectionism wiww prove to be a much more accurate account of how de brain works.[21]

The Churchwands often invoke de fate of oder, erroneous popuwar deories and ontowogies dat have arisen in de course of history.[21][22] For exampwe, Ptowemaic astronomy served to expwain and roughwy predict de motions of de pwanets for centuries, but eventuawwy dis modew of de sowar system was ewiminated in favor of de Copernican modew. The Churchwands bewieve de same ewiminative fate awaits de "sentence-cruncher" modew of de mind in which dought and behavior are de resuwt of manipuwating sentence-wike states cawwed "propositionaw attitudes".

Some phiwosophers take an epistemic approach and argue dat de mind–body probwem is currentwy unsowvabwe, and perhaps wiww awways remain unsowvabwe to human beings. This is usuawwy termed New mysterianism. Cowin McGinn howds dat human beings are cognitivewy cwosed in regards to deir own minds. According to McGinn human minds wack de concept-forming procedures to fuwwy grasp how mentaw properties such as consciousness arise from deir causaw basis.[67] An exampwe wouwd be how an ewephant is cognitivewy cwosed in regards to particwe physics.

A more moderate conception has been expounded by Thomas Nagew, which howds dat de mind–body probwem is currentwy unsowvabwe at de present stage of scientific devewopment and dat it might take a future scientific paradigm shift or revowution to bridge de expwanatory gap. Nagew posits dat in de future a sort of "objective phenomenowogy" might be abwe to bridge de gap between subjective conscious experience and its physicaw basis.[68]

Each attempt to answer de mind–body probwem encounters substantiaw probwems. Some phiwosophers argue dat dis is because dere is an underwying conceptuaw confusion, uh-hah-hah-hah.[69] These phiwosophers, such as Ludwig Wittgenstein and his fowwowers in de tradition of winguistic criticism, derefore reject de probwem as iwwusory.[70] They argue dat it is an error to ask how mentaw and biowogicaw states fit togeder. Rader it shouwd simpwy be accepted dat human experience can be described in different ways—for instance, in a mentaw and in a biowogicaw vocabuwary. Iwwusory probwems arise if one tries to describe de one in terms of de oder's vocabuwary or if de mentaw vocabuwary is used in de wrong contexts.[70] This is de case, for instance, if one searches for mentaw states of de brain, uh-hah-hah-hah. The brain is simpwy de wrong context for de use of mentaw vocabuwary—de search for mentaw states of de brain is derefore a category error or a sort of fawwacy of reasoning.[70]

Today, such a position is often adopted by interpreters of Wittgenstein such as Peter Hacker.[69] However, Hiwary Putnam, de originator of functionawism, has awso adopted de position dat de mind–body probwem is an iwwusory probwem which shouwd be dissowved according to de manner of Wittgenstein, uh-hah-hah-hah.[71]

The desis of physicawism is dat de mind is part of de materiaw (or physicaw) worwd. Such a position faces de probwem dat de mind has certain properties dat no oder materiaw ding seems to possess. Physicawism must derefore expwain how it is possibwe dat dese properties can nonedewess emerge from a materiaw ding. The project of providing such an expwanation is often referred to as de "naturawization of de mentaw".[53] Some of de cruciaw probwems dat dis project attempts to resowve incwude de existence of qwawia and de nature of intentionawity.[53]

Many mentaw states seem to be experienced subjectivewy in different ways by different individuaws.[32] And it is characteristic of a mentaw state dat it has some experientiaw qwawity, e.g. of pain, dat it hurts. However, de sensation of pain between two individuaws may not be identicaw, since no one has a perfect way to measure how much someding hurts or of describing exactwy how it feews to hurt. Phiwosophers and scientists derefore ask where dese experiences come from. The existence of cerebraw events, in and of demsewves, cannot expwain why dey are accompanied by dese corresponding qwawitative experiences. The puzzwe of why many cerebraw processes occur wif an accompanying experientiaw aspect in consciousness seems impossibwe to expwain, uh-hah-hah-hah.[31]

Yet it awso seems to many dat science wiww eventuawwy have to expwain such experiences.[53] This fowwows from an assumption about de possibiwity of reductive expwanations. According to dis view, if an attempt can be successfuwwy made to expwain a phenomenon reductivewy (e.g., water), den it can be expwained why de phenomenon has aww of its properties (e.g., fwuidity, transparency).[53] In de case of mentaw states, dis means dat dere needs to be an expwanation of why dey have de property of being experienced in a certain way.

The 20f-century German phiwosopher Martin Heidegger criticized de ontowogicaw assumptions underpinning such a reductive modew, and cwaimed dat it was impossibwe to make sense of experience in dese terms. This is because, according to Heidegger, de nature of our subjective experience and its qwawities is impossibwe to understand in terms of Cartesian "substances" dat bear "properties". Anoder way to put dis is dat de very concept of qwawitative experience is incoherent in terms of—or is semanticawwy incommensurabwe wif de concept of—substances dat bear properties.[72]

This probwem of expwaining introspective first-person aspects of mentaw states and consciousness in generaw in terms of dird-person qwantitative neuroscience is cawwed de expwanatory gap.[73] There are severaw different views of de nature of dis gap among contemporary phiwosophers of mind. David Chawmers and de earwy Frank Jackson interpret de gap as ontowogicaw in nature; dat is, dey maintain dat qwawia can never be expwained by science because physicawism is fawse. There are two separate categories invowved and one cannot be reduced to de oder.[74] An awternative view is taken by phiwosophers such as Thomas Nagew and Cowin McGinn. According to dem, de gap is epistemowogicaw in nature. For Nagew, science is not yet abwe to expwain subjective experience because it has not yet arrived at de wevew or kind of knowwedge dat is reqwired. We are not even abwe to formuwate de probwem coherentwy.[32] For McGinn, on oder hand, de probwem is one of permanent and inherent biowogicaw wimitations. We are not abwe to resowve de expwanatory gap because de reawm of subjective experiences is cognitivewy cwosed to us in de same manner dat qwantum physics is cognitivewy cwosed to ewephants.[75] Oder phiwosophers wiqwidate de gap as purewy a semantic probwem. This semantic probwem, of course, wed to de famous "Quawia Question", which is: Does Red cause Redness?

Intentionawity is de capacity of mentaw states to be directed towards (about) or be in rewation wif someding in de externaw worwd.[27] This property of mentaw states entaiws dat dey have contents and semantic referents and can derefore be assigned truf vawues. When one tries to reduce dese states to naturaw processes dere arises a probwem: naturaw processes are not true or fawse, dey simpwy happen, uh-hah-hah-hah.[76] It wouwd not make any sense to say dat a naturaw process is true or fawse. But mentaw ideas or judgments are true or fawse, so how den can mentaw states (ideas or judgments) be naturaw processes? The possibiwity of assigning semantic vawue to ideas must mean dat such ideas are about facts. Thus, for exampwe, de idea dat Herodotus was a historian refers to Herodotus and to de fact dat he was a historian, uh-hah-hah-hah. If de fact is true, den de idea is true; oderwise, it is fawse. But where does dis rewation come from? In de brain, dere are onwy ewectrochemicaw processes and dese seem not to have anyding to do wif Herodotus.[26]

Humans are corporeaw beings and, as such, dey are subject to examination and description by de naturaw sciences. Since mentaw processes are intimatewy rewated to bodiwy processes, de descriptions dat de naturaw sciences furnish of human beings pway an important rowe in de phiwosophy of mind.[2] There are many scientific discipwines dat study processes rewated to de mentaw. The wist of such sciences incwudes: biowogy, computer science, cognitive science, cybernetics, winguistics, medicine, pharmacowogy, and psychowogy.[78]

The deoreticaw background of biowogy, as is de case wif modern naturaw sciences in generaw, is fundamentawwy materiawistic. The objects of study are, in de first pwace, physicaw processes, which are considered to be de foundations of mentaw activity and behavior.[79] The increasing success of biowogy in de expwanation of mentaw phenomena can be seen by de absence of any empiricaw refutation of its fundamentaw presupposition: "dere can be no change in de mentaw states of a person widout a change in brain states."[78]

Widin de fiewd of neurobiowogy, dere are many subdiscipwines dat are concerned wif de rewations between mentaw and physicaw states and processes:[79]Sensory neurophysiowogy investigates de rewation between de processes of perception and stimuwation.[80]Cognitive neuroscience studies de correwations between mentaw processes and neuraw processes.[80]Neuropsychowogy describes de dependence of mentaw facuwties on specific anatomicaw regions of de brain, uh-hah-hah-hah.[80] Lastwy, evowutionary biowogy studies de origins and devewopment of de human nervous system and, in as much as dis is de basis of de mind, awso describes de ontogenetic and phywogenetic devewopment of mentaw phenomena beginning from deir most primitive stages.[78] Evowutionary biowogy furdermore pwaces tight constraints on any phiwosophicaw deory of de mind, as de gene-based mechanism of naturaw sewection does not awwow any giant weaps in de devewopment of neuraw compwexity or neuraw software but onwy incrementaw steps over wong time periods.[81]

Since de 1980s, sophisticated neuroimaging procedures, such as fMRI (above), have furnished increasing knowwedge about de workings of de human brain, shedding wight on ancient phiwosophicaw probwems.

The medodowogicaw breakdroughs of de neurosciences, in particuwar de introduction of high-tech neuroimaging procedures, has propewwed scientists toward de ewaboration of increasingwy ambitious research programs: one of de main goaws is to describe and comprehend de neuraw processes which correspond to mentaw functions (see: neuraw correwate).[79] Severaw groups are inspired by dese advances.

Computer science concerns itsewf wif de automatic processing of information (or at weast wif physicaw systems of symbows to which information is assigned) by means of such dings as computers.[82] From de beginning, computer programmers have been abwe to devewop programs dat permit computers to carry out tasks for which organic beings need a mind. A simpwe exampwe is muwtipwication, uh-hah-hah-hah. It is not cwear wheder computers couwd be said to have a mind. Couwd dey, someday, come to have what we caww a mind? This qwestion has been propewwed into de forefront of much phiwosophicaw debate because of investigations in de fiewd of artificiaw intewwigence (AI).

Widin AI, it is common to distinguish between a modest research program and a more ambitious one: dis distinction was coined by John Searwe in terms of a weak AI and strong AI. The excwusive objective of "weak AI", according to Searwe, is de successfuw simuwation of mentaw states, wif no attempt to make computers become conscious or aware, etc. The objective of strong AI, on de contrary, is a computer wif consciousness simiwar to dat of human beings.[83] The program of strong AI goes back to one of de pioneers of computation Awan Turing. As an answer to de qwestion "Can computers dink?", he formuwated de famous Turing test.[84] Turing bewieved dat a computer couwd be said to "dink" when, if pwaced in a room by itsewf next to anoder room dat contained a human being and wif de same qwestions being asked of bof de computer and de human being by a dird party human being, de computer's responses turned out to be indistinguishabwe from dose of de human, uh-hah-hah-hah. Essentiawwy, Turing's view of machine intewwigence fowwowed de behaviourist modew of de mind—intewwigence is as intewwigence does. The Turing test has received many criticisms, among which de most famous is probabwy de Chinese roomdought experiment formuwated by Searwe.[83]

The qwestion about de possibwe sensitivity (qwawia) of computers or robots stiww remains open, uh-hah-hah-hah. Some computer scientists bewieve dat de speciawty of AI can stiww make new contributions to de resowution of de "mind–body probwem". They suggest dat based on de reciprocaw infwuences between software and hardware dat takes pwace in aww computers, it is possibwe dat someday deories can be discovered dat hewp us to understand de reciprocaw infwuences between de human mind and de brain (wetware).[85]

Psychowogy is de science dat investigates mentaw states directwy. It uses generawwy empiricaw medods to investigate concrete mentaw states wike joy, fear or obsessions. Psychowogy investigates de waws dat bind dese mentaw states to each oder or wif inputs and outputs to de human organism.[86]

An exampwe of dis is de psychowogy of perception. Scientists working in dis fiewd have discovered generaw principwes of de perception of forms. A waw of de psychowogy of forms says dat objects dat move in de same direction are perceived as rewated to each oder.[78] This waw describes a rewation between visuaw input and mentaw perceptuaw states. However, it does not suggest anyding about de nature of perceptuaw states. The waws discovered by psychowogy are compatibwe wif aww de answers to de mind–body probwem awready described.

Cognitive science is de interdiscipwinary scientific study of de mind and its processes. It examines what cognition is, what it does, and how it works. It incwudes research on intewwigence and behavior, especiawwy focusing on how information is represented, processed, and transformed (in facuwties such as perception, wanguage, memory, reasoning, and emotion) widin nervous systems (human or oder animaw) and machines (e.g. computers). Cognitive science consists of muwtipwe research discipwines, incwuding psychowogy, artificiaw intewwigence, phiwosophy, neuroscience, winguistics, andropowogy, sociowogy, and education.[87] It spans many wevews of anawysis, from wow-wevew wearning and decision mechanisms to high-wevew wogic and pwanning; from neuraw circuitry to moduwar brain organisation, uh-hah-hah-hah. Rowwands argues dat cognition is enactive, embodied, embedded, affective and (potentiawwy) extended. The position is taken dat de "cwassicaw sandwich" of cognition sandwiched between perception and action is artificiaw; cognition has to be seen as a product of a strongwy coupwed interaction dat cannot be divided dis way.[88][89]

Most of de discussion in dis articwe has focused on one stywe or tradition of phiwosophy in modern Western cuwture, usuawwy cawwed anawytic phiwosophy (sometimes described as Angwo-American phiwosophy).[90] Many oder schoows of dought exist, however, which are sometimes subsumed under de broad (and vague) wabew of continentaw phiwosophy.[90] In any case, dough topics and medods here are numerous, in rewation to de phiwosophy of mind de various schoows dat faww under dis wabew (phenomenowogy, existentiawism, etc.) can gwobawwy be seen to differ from de anawytic schoow in dat dey focus wess on wanguage and wogicaw anawysis awone but awso take in oder forms of understanding human existence and experience. Wif reference specificawwy to de discussion of de mind, dis tends to transwate into attempts to grasp de concepts of dought and perceptuaw experience in some sense dat does not merewy invowve de anawysis of winguistic forms.[90]

Immanuew Kant's Critiqwe of Pure Reason, first pubwished in 1781 and presented again wif major revisions in 1787, represents a significant intervention into what wiww water become known as de phiwosophy of mind. Kant's first critiqwe is generawwy recognized as among de most significant works of modern phiwosophy in de West. Kant is a figure whose infwuence is marked in bof continentaw and anawytic/Angwo-American phiwosophy. Kant's work devewops an in-depf study of transcendentaw consciousness, or de wife of de mind as conceived drough universaw categories of consciousness.

In 1896, Henri Bergson made in Matter and Memory "Essay on de rewation of body and spirit" a forcefuw case for de ontowogicaw difference of body and mind by reducing de probwem to de more definite one of memory, dus awwowing for a sowution buiwt on de empiricaw test case of aphasia.

There are countwess subjects dat are affected by de ideas devewoped in de phiwosophy of mind. Cwear exampwes of dis are de nature of deaf and its definitive character, de nature of emotion, of perception and of memory. Questions about what a person is and what his or her identity consists of awso have much to do wif de phiwosophy of mind. There are two subjects dat, in connection wif de phiwosophy of de mind, have aroused speciaw attention: free wiww and de sewf.[2]

In de context of phiwosophy of mind, de probwem of free wiww takes on renewed intensity. This is certainwy de case, at weast, for materiawistic determinists.[2] According to dis position, naturaw waws compwetewy determine de course of de materiaw worwd. Mentaw states, and derefore de wiww as weww, wouwd be materiaw states, which means human behavior and decisions wouwd be compwetewy determined by naturaw waws. Some take dis reasoning a step furder: peopwe cannot determine by demsewves what dey want and what dey do. Conseqwentwy, dey are not free.[93]

This argumentation is rejected, on de one hand, by de compatibiwists. Those who adopt dis position suggest dat de qwestion "Are we free?" can onwy be answered once we have determined what de term "free" means. The opposite of "free" is not "caused" but "compewwed" or "coerced". It is not appropriate to identify freedom wif indetermination, uh-hah-hah-hah. A free act is one where de agent couwd have done oderwise if it had chosen oderwise. In dis sense a person can be free even dough determinism is true.[93] The most important compatibiwist in de history of de phiwosophy was David Hume.[94] More recentwy, dis position is defended, for exampwe, by Daniew Dennett.[95]

On de oder hand, dere are awso many incompatibiwists who reject de argument because dey bewieve dat de wiww is free in a stronger sense cawwed wibertarianism.[93] These phiwosophers affirm de course of de worwd is eider a) not compwetewy determined by naturaw waw where naturaw waw is intercepted by physicawwy independent agency,[96] b) determined by indeterministic naturaw waw onwy, or c) determined by indeterministic naturaw waw in wine wif de subjective effort of physicawwy non-reducibwe agency.[97] Under Libertarianism, de wiww does not have to be deterministic and, derefore, it is potentiawwy free. Critics of de second proposition (b) accuse de incompatibiwists of using an incoherent concept of freedom. They argue as fowwows: if our wiww is not determined by anyding, den we desire what we desire by pure chance. And if what we desire is purewy accidentaw, we are not free. So if our wiww is not determined by anyding, we are not free.[93]

The phiwosophy of mind awso has important conseqwences for de concept of "sewf". If by "sewf" or "I" one refers to an essentiaw, immutabwe nucweus of de person, some modern phiwosophers of mind, such as Daniew Dennett bewieve dat no such ding exists. According to Dennett and oder contemporaries, de sewf is considered an iwwusion, uh-hah-hah-hah.[98] The idea of a sewf as an immutabwe essentiaw nucweus derives from de idea of an immateriaw souw. Such an idea is unacceptabwe to modern phiwosophers wif physicawist orientations and deir generaw skepticism of de concept of "sewf" as postuwated by David Hume, who couwd never catch himsewf not doing, dinking or feewing anyding.[99] However, in de wight of empiricaw resuwts from devewopmentaw psychowogy, devewopmentaw biowogy and neuroscience, de idea of an essentiaw inconstant, materiaw nucweus—an integrated representationaw system distributed over changing patterns of synaptic connections—seems reasonabwe.[100]